Thermomagnetic imaging method

ABSTRACT

The magentic image receiving surface of a copying apparatus is provided with a layer of FeRh or an analogous ingredient which is antiferromagnetic above and below its Neel temperature but exhibits a pronounced coercive force at the Neel temperature. The image receiving surface is moved past an exposure station to receive a thermal image of an original. The exposing step may involve heating selected areas of the image receiving surface to Neel temperature in accordance with the image pattern of the original or heating selected areas of the image receiving surface to above the Neel temperature while the remaining areas remain at Neel temperature. The resulting thermal image is converted with magnetic toner into a powder image, either on the image receiving surface or upon transfer onto an auxiliary surface, and the powder image is transferred onto and fused to paper or another transfer material.

United States Patent 2 [191 Kohlmannsperger [451 Feb. 12, 1974 I THERMOMAGNETIC IMAGING METHOD [75] Inventor: Josef Kohlmannsperger, Munich,

Germany 22 Filed: Nov. 3, 1971 21 Appl. No.: 195,338

[30] Foreign Application Priority Data Nov. 4, 1970 Germany U 2054117[52] US. Cl 117/175, 117/237, 117/240, 250/316, 346/1, 346/74 MT [51 IInt. Cl. G03g 17/00, 003g 19/00 [58] Field of Search 117/237, 240, 17.5;346/1, 346/74 MT; 250/65 T [56] References Cited UNITED STATES PATENTS3,472,695 10/1969 Kaufer et al. l17/l7.5 3,562,760 2/1971 Cushner et al.250/65 T 3,566,786 3/1971 Kaufer et al. 117/l7.5

3,582,877 6/1971 Benoit t 250/65 T 3,598,993 8/1971 Kaufer et a1. 250/65T 3,613,100 10/1971 Kaufer et a1. 1l7/17.5

Primary Examiner-William D. Martin Assistant ExaminerM. SofocleousAttorney, Agent, or FirmMichael S. Striker [5 7 ABSTRACT The magenticimage receiving surface of a copying apparatus is provided with a layerof FeRh or an analogous ingredient which is antiferromagnetic above andbelow its Neel temperature but exhibits a pronounced coercive force atthe Neel temperature. The image receiving surface is moved past anexposure station to receive a thermal image of an original. The exposingstep may involve heating selected areas of the image receiving surfaceto Neel temperature in accordance with the image pattern of the originalor heating selected areas of the image receiving surface to above theNeel temperature while the remaining areas re main at Neel temperature.The resulting thermal image is converted with magnetic toner into apowder image, either on the image receiving surface or upon transferonto an auxiliary surface, and the powder image is transferred onto andfused to paper or another transfer material.

10 Claims, 4 Drawing Figures PA TE'NIEB FEB l 2 I974 SHEET 2 BF 3.

PAIE'NIED FEB I 2 I874 SHEH 3 OF 3 1 THERMOMAGNETIC IMAGING METHODBACKGROUND OF THE INVENTION The present invention relates to a method ofmaking copies of images of originals by the magnetic imaging process,and more particularly to improvements in a method of converting thermalimages of originals into powder images prior to transfer and fixing ofsuch powder images to paper or other transfer material.

It is already known to produce a magnetic image of an original byapplying to a uniformly premagnetized surface a thermal image whereinthe temperature of certain portions exceeds the Curie point. Suchmagnetic images can be converted into powder images by utilizing amagnetic toner. It is further known to subject a layer of magnetizabletoner to the action of an external magnetic field and to simultaneouslyexpose onto the magnetizable toner a thermal image wherein thetemperature of certain portions exceeds the Curie point. This bringsabout a selective removal or transfer of pulverulent toner so that theresidual toner or the removed toner forms a powder image. It was alsoproposed to bring a magnetic layer in contact with a control layerwherein certain portions are heated above the Curie point to thusprovide on the magnetic layer a permanent magnetic image of theoriginal. A drawback of all such conventional proposals is that theimage receiving layer must be subjected to the action of an externalmagnetic field either prior to or during the application of thermalimages.

SUMMARY OF THE INVENTION An object of the invention is to provide anovel and improved method of making thermal images of originals onmagnetic image receiving surfaces and of converting such thermal imagesinto powder images.

Another object of the invention is to provide a novel magnetic imagingor copying method according to which the image receiving surface neednot be subjected to the action of external magnetic fields, either priorto or during the formation of thermal images.

A further object of the invention is to provide a novel and improvedimage receiving surface for reception and retention of thermal images inapparatus wherein the images are developed by resorting to magnetictoner particles.

An additional object of the invention is to provide a method accordingto which a thermal image can be converted into'a powder image as oftenas desired or necessary.

One feature of the present invention resides in the provision of amethod of reproducing images of originals on paper or other suitabletransfer material. The method comprises the steps of exposing a thermalimage of an original on an image receiving surface containing aningredient (e.g., FeRh, MnAs, MnTe or Cr O which is antiferromagnetic attemperatures above and below its Neel temperature (T and which exhibitsa pronounced coercive force (H at the Neel temperature by changing thetemperature of the surface in accordance with the image pattern of theoriginal so that the surface exhibits first areas which are maintainedat Neel temperature and second areas which are maintained at other thanNeel temperature (i.e., above or below T and converting the thermalimage into a powder image, either on the image receiving surface orsubsequent to transfer of the thermal image onto an auxiliary surface.

If the ingredient of the image receiving surface is maintained at lessthan Neel temperature prior to the exposing step, the temperaturechanging step comprises heating the first areas of the surface to Neeltemperatures; the other temperature is then preferably substantiallybelow Neel temperature, e.g.. at room temperature.

If the ingredient of the image receiving surface is maintained at Neeltemperature prior to the exposing step, the temperature changing stepcomprises heating the second areas of the surface to above Neeltemperature so that the other temperature substantially exceeds It isoften desirable to maintain the temperature of the image receivingsurface prior to the exposing step at a temperature which closelyapproximates the temperature of one of the first and second areas uponcom pletion of the temperature changing step.

The powder image can be transferred onto and fixed or stabilized onpaper or other suitable transfer material.

In accordance with a more specific feature of my method, the convertingstep may comprise contacting the exposed image receiving surface with acoat of a pulverulent magnetic toner from which the surface removestoner so that the thus removed toner adheres to the first areas of thesurface.

Alternatively, the thermal image can be transferred onto a magneticlayer whose coercive force is less than the coercive force of theingredient of the image receiving surface at T the converting step thencomprises placing the transferred thermal image at least once intocontact with a pulverulent magnetic toner to thereby convert thetransferred thermal image into a powder image which can be transferredonto paper or the like.

The toner may consist of magnetizable carriers and a pigmentizedthermoplastic material which can be fused to the transfer material inresponse to the application of heat. Such thermoplastic materials andmagnetizable carriers therefor are well known in the art.

The novel features which are considered as characteristic of theinvention are set forth in particular in the appended claims. Theapparatus itself, however, both as to its construction and its mode ofoperation, together with additional features and advantages of themethod, will be best understood upon perusal of the following detaileddescription of certain specific embodiments with reference to theaccompanying draw- BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a diagramshowing the dependency of coercive force of FeRh on changes intemperature;

FIG. 2 is a partly elevational and partly vertical sec tional view of afirst apparatus wherein the image receiving surface serves for theformation of thermal and powder images as well as for the transfer ofpowder images onto a sheet-like carrier;

FIG. 3 is a partly elevational and partly vertical sectional view of asecond apparatus wherein the formation of thermal and powder imagestakes place on two separate surfaces; and

FIG. 4 is a partly elevational and partly vertical sectional view of anapparatus which constitutes a modification of the apparatus shown inFIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The diagram of FIG. 1illustrates the dependency of coercive force (magnetic field) H of FeRhon the temperature. Reference may be had to an article by Stoffelappearing on page 1,239 of V]. 40, No. 3 of Journal of Applied Physics.The diagram indicates that the antiferromagnetic FeRh compound exhibitsno coercive force at a temperature T which corresponds to or approachesthe ambient temperature. When the compound is heated to 60C (this is theNeel temperature T of FeRh), the coercive force H increases abruptly toa value well in excess of 120Acm*. In response'to further heating to atemperature which exceeds T the coercive force H decreases steeply and,at a temperature T slightly in excess of 100C, decreases to a value atwhich a magnetic toner having an appropriate particle size, coerciveforce or permeability cannot adhere to an image receiving surfacecontaining FeRh.

The copying apparatus of FIG. 2 comprises a drumshaped image receivingsurface 2 whose exterior is provided with a layer 1 of FeRh. Successiveincrements of the layerl travel along a development station containing adispenser 3 for a magnetic toner, e.g., finely divided ferrite powder ofthe type sold under the trade name Keraperm 417, having a coercive forceof 0.16 Acm and an initial permeability of 2,400. The particles of suchtoner are coated with a suitable synthetic thermoplastic materialcontaining a desired type of pigment. The development station is locatedahead of a drum cleaning station which includes a rotary brush 4 and areceptacle 5 serving to collect surplus toner which is removed from thelayer 1 by the brush 4. An exposure station which is located upstream ofthe development station (see the arrow A which indicates the directionof rotation of the drum 2) includes an objective 6 which focusses theimages of successive increments of a moving original 7 onto successiveincrements of the layer 1 so that the latter is provided with a, thermalimage of the original. A radiation heater 8 behind the path of theoriginal 7 emits radiant energy which passes through the original andimpinges on the layer 1. The direction in which the original 7 is beingmoved at the exact peripheral speed of the drum 2 is indicated by thearrow B. It is clear that the illustrated exposure station constitutesbut one of several available means for producing a thermal image on thelayer 1. For example, the original can be brought in direct contact withthe layer 1 or the latter can receive a thermal image by resorting to anepiscopic procedure.

Those increments of the layer 1 which advance beyond the developmentstation (dispenser 3) are caused to pass along a transfer roller 9 whichpresses against the layer 1 successive increments of a sheetor striporweb-like transfer material 11 (e.g., normal writing paper). Suchmaterial 11 is stored on a roll and is being withdrawn from the roll bypairs of advancing rollers 12, 13 and 14, 15. The transfer material 11receives from the layer 1 a powder image which is formed at thedevelopment station, and such powder image is thereupon stabilized by afuser 16 which heats the toner so that the thermoplastic material on theparticles of toner is caused to melt and penetrates into the material ofthe strip 11. The direction in which the rollers 12-15 advance the strip11 is indicated by the arrow C.

The drum 2 is hollow and its interior accommodates a thermostaticallycontrolled heater 17 which maintains the layer 1 at the temperature T Asstated above, the Neel temperature of FeRh is 60C.

The operation:

The drive means (including a shaft 2a for rotating the drum 2 in thedirection indicated by the arrow A) rotates the layer 1 at a speed whichequals the speed of the original 7 (arrow B). The heater 17 is on andmaintains those increments of the layer 1 which approach the exposurestation (objective 6) at a temperature of 60C. so that the coerciveforce He of the layer I greatly exceeds Acm. Those portions of the layer1 which register with the image-free (brighter) portions of the original7 are heated by the heater 8 to a temperature correspondingsubstantially to the temperature T of FIG. 1. Consequently, suchportions of the layer 1 exhibit a greatly reduced coercive force whichis so weak that they cannot retain toner during travel past thedevelopment station (dispenser 3). The layer portions exhibiting agreater coercive force accept and retain toner so that the thermal imageformed at the station including the objective 6 is converted into apositive powder image of the original 7. Such powder image istransferred onto the strip 11 by the roller 9 and is thereuponstabilized by the fuser 16. The surplus of toner is removed from thelayer 1 by the revolving cleaning brush 4 to accumulate in thereceptacle 5. A blower 18 or an analogous cooling device is locateddownstream of the brush 4 to cool successive increments of the layer 1before such increments reach the exposure station. The heater 17 insuresthat the temperature of successive increments of the layer 1 which reachthe exposure station (objective 6) equals T At this temperature, thelayer 1 exhibits uniform magnetic properties.

It will be noted that the apparatus of FIG. 2 forms a positive powderimage because selected portions of the layer 1 are heated above T duringtravel past the exposure station whereby the thus heated portions cannotretain toner during travel past the development station. The remainingportions of the layer 1 can accept and retain toner because theirtemperature equals or closely approximates T due to the provision ofheater 17. The formation of a positive powder image is due to the factthat the magneticproperties of FeRh change abruptly in response toheating above T The cooling device 18 insures that the thermal image iserased even if the shaft 2a is caused to rotate the drum 2 at asubstantial speed so that the formation of successive thermal images canbe carried out at frequent intervals. Thus, the cooling action of thedevice 18 must be sufficient to insure, in combination with the heater17, that each increment of the layer 1 which reaches the exposurestation is maintained at or close to T FIG. 3 illustrates a secondapparatus wherein the drum-shaped image receiving surface 2 is againprovided with a layer 1 of FelRh. The layer 1 is contacted by a uniformpremagnetized coat 20 of toner which is applied to the periphery of anauxiliary drum or donor surface 19 rotating in the direction indicatedby the arrow D. The coercive force H of toner which forms the coat 20exceeds the coercive force of the layer 1.

The exposure station including the parts 6, 8 and a transportingmechanism for the original 7 is identical with or similar to theexposure station of the apparatus shown in FIG. 2. The thermal imagewhich is exposed onto the layer 1 in the region of the exposure stationis thereupon converted into a negative powder image during travel ofsuccessive increments of the layer 1 past the line of contact with thecoat 20 on the auxiliary drum 19. The toner which forms the negativepowder image on the layer 1 is caused to descend into a receptacle 5 ata cooling station which accommodates a suit able blower 18. This insuresthat all portions'of the layer 1 which return into register with theobjective 6 are free of toner.

The development station is located in the region of contact of the layerII with the coat 20. Such coat of toner is applied by a dispenser 3which includes a magazine or hopper for toner and a rotating brush whichsprinkles the toner onto the surface of the auxiliary drum 19 to formthereon the coat 20. The transfer roller 9 presses successive incrementsof strip-shaped transfer material 11 against successive increments ofthe positive powder image on the drum l9 downstream of the developmentstation. The transfer material 11 is being withdrawn from a roll and isbeing transported in the direction indicated by arrow C by two pairs ofadvancing rollers 12, 13 and 14, 15. The reference character M denotes afuser which heats the powder image on the transfer material 11 beforethe material leaves the copying apparatus. It will be noted that theheater 17 of FIG. 2 is omitted in the apparatus of FIG.

Due to absence of the heater 17, the layer 1 is maintained at atemperature (T which corresponds to the temperature of surrounding air.Therefore, the material of the layer 1 does not exhibit any outwardlyeffective magnetic moments. The intensity of the source 8 of radiationenergy is selected in such a way that all portions of the layer 1 whichregister with image-free portions of the moving original 7 are heated tothe Neeltempe'rature T Thus, the thermal image which is produced on thelayer 1 at the exposure station is a negative image of the original.

As the drum 2 continues to rotate in the direction indicated by thearrow A, the layer 1 rolls in contact with successive increments of thecoat on the periphery of the auxiliary drum 19 whereby the negativethermal image is converted into a negative powder image. In other words,those portions of the layer 1 which are heated to the temperature Tattract the toner of the coat 20 whereby the remainder of such coatconstitutes a positive powder image of the original '7. The periphery ofthe auxiliary drum H9 is magnetized with a high degree of uniformity andreceives toner during travel past the dispenser 3. The magnetized layerof the drum 19 is indicated at 20a.

The positive powder image which remains on the layer 19a downstream ofthe point of contact between the layer 1 and the coat 20 is thereupontransferred onto the strip 11 by the roller 9, and such image is fixedby heat which is furnished by* the fuser 16. As mentioned before, thenegative powder image on the layer 1 of the drum 2 is destroyed duringtravel past the nozzle of the cooling device 18 so that the tonerdescends into the receptacle 5. Such destruction of the negative powderimage is due to the fact that air or another coolant issuing from thecooling device 18 reduces the temperature of all portions of the layer lto less than T i.e., the coercive force H, of the layer 1 decreases sothat the latter cannot retain the toner which forms the negative powderimage.

The copying apparatus of FIG. 4 includes a hollow drum-shaped imagereceiving surface 2 provided with a layer ll of FeRh and containing aheater 17 which heats successive increments of the layer to atemperature T not later than when such increments reach the exposurestation including an objective 6, a radiation heater 8 and a mechanismfor transporting the original 7 in the direction indicated by the arrowB. A cooling device 18 is adjacent to the layer ll upstream of theexposure station. The speed of lengthwise movement of the original 7equals or closely approximates the speed at which the drum 2 rotates thelayer I in the direction indicated by the arrow A.

The drum 2 cooperates with an auxiliary drum 21 which is rotatable inthe direction indicated by arrow E about the axis of a shaft 2llamounted on a lever 24 which is fulcrumed at 23 and can be pivotedbetween the solid-line and broken-line positions of FIG. 4 torespectively move a magnetic layer 22 on the periphery of the auxiliarydrum 21 into contact with the transfer material lil or with the layer 1.The coercive force H of the magnetic layer 22 on the auxiliary drum 2]is less than the coercive force of the layer 1 at the temperature T Forexample, the layer 22 may consist of black iron oxide of the type knownas SM and produced by Bayer-Werke, Western Germany. The coercive forceof such layer may be in the range of Acm". A dispenser 3 for tonercontains a revolving brush 3a which sprinkles particles of toner ontothe layer 22 of the auxiliary drum 21. A cleaning station downstream ofthe transfer roller 9 includes a driven brush 4 and a receptacle 5 forsurplus toner. The apparatus further comprises a demagnetizing device 25for the layer 22. The parts 12-116 of the apparatus shown in FIG. 4correspond to similarly referenced parts of the apparatus shown in FIGS.2 or 3.

The operation:

The heater 117 insures that the temperature of successive increments ofthe layer l which reach the exposure station (objective 6) at leastapproximates 60C, i.e., the Neel-temperature of FeRh. Thus, thoseportions of the layer l which are in register with image-free portionsof the original 7 are heated to above the temperature T whereby thecoercive force of such layer portions decreases well below 120 Acm. Thelayer 1 carries a positive thermal or magnetic image of the original 7toward the point of contact with the layer 22 which is assumed to bemaintained by lever 2d and auxiliary drum 2B in the broken-line positionof FIG. 4. The magnetic image of the layer l is transferred onto thelayer 22. Such transfer of the magnetic image from the layer 1 onto thelayer 22 is due to magnetization of selected portions of the layer 22 bythose portions of the layer I which are maintained at the temperature TThe lever 24 is thereupon pivoted in the direction indicated by thearrow F so as to disengage the layer 22 from the layer 1 and to causesuccessive increments of the magnetic image to travel past thedevelopment station where the magnetic image is converted into apositive powder image by toner which is sprinkled by the brush 3a. Suchpowder image is transferred onto the material Ill by the roller 9 andthe surplus toner is removed by the cleaning brush 4 to enter thereceptacle 5. The powder image is stabilized on the transfer material 11during travel past the fuser 16 under the action of the advancingrollers 12-15 (see the arrow C). The development and transfer ofmagnetic image on the layer 22 of the auxiliary drum 21 can be repeatedas often as desired, i.e., the apparatus can make any desired number ofcopies simply by maintaining the drum 21 in the solid-line position ofFIG. 4 and causing its shaft 21a to rotate in the direction indicated bythe arrow B.

When the desired number of copies is completed, the

. demagnetizing device 25 is activated to destroy the magnetic image onthe layer 22 and the lever 24 is pivoted to the broken-line position soas to return the layer 22 into contact with the layer 11. The layer 22is then ready to receive the positive magnetic image of a furtheroriginal.

The method which can be carried out with the apparatus of the presentinvention is based on the recognition that a thermal image of anoriginal can be obtained by employing a magnetic image receiving surfacewhich contains an antiferromagnetic compound or ingredient and byheating selected portions of the image receiving surface to atemperature which exceeds the Neel temperature of the antiferromagneticcompound. Such compound may butneed not be FeRh;

The magnetic moments of FeRh and analogous antiferromagnetic compoundsare such that they do not exhibit an outwardly acting permanent magneticmo ment. Thus, as a result of their antiparallel positions, the magneticmoments of antiferromagnetic compounds cancel or neutralize each other.The relatively small positive susceptibility of antiferromagneticcompounds rises to a maximum value at a temperature at which theexchange forces become incapable of maintaining the magnetic moments inpositions of alignment against the thermal movements. At suchtemperature, i.e., at the Neel-temperature (T the antiferromagneticcompound becomes ferromagnetic or paramagnetic. These characteristicsare exhibited by almost all inorganic compositions containing transitionmetals, rare earths, actinium, chromium, manganese, platinum, palladiumand other rare metals. The method of the present invention preferablyemploys such antiferromagnetic compounds whose Neel-temperature is onlyslightly above room temperature. These materials include MnTe (T +34C),MnAs (T +43C.), Cr O (T +47C.) and FeRh (T +60C.).

An advantage of such antiferromagnetic compounds is that, when used in amagnetic image receiving surface, the latter can receive a thermal imagewithout resorting to an external magnetic field. Such compounds arenon-magnetic at a temperature which is below the Neel-temperature buttheir coercive force rises abruptly at T to reach a considerable valueand decreases rapidly to a negligible value if the temperature risesabove T Consequently, an image receiving surface employing suchcompounds exhibits a steep gradation to allow the exposure of thermalimages which are rich in contrasts.

The conversion of antiferromagnetic properties of such compounds intoferromagnetic or paramagnetic properties is accompanied by abnormalchanges in specific heat. Thus, when the temperature approaches T thespecific heat rises approximately by one order of magnitude and dropsrapidly when the Neeltemperature is exceeded to reassume its originallow compound (FIG. 3)-or from T to a higher temperature (FIGS. 2 and 4).In each instance, it is advisable to maintain the starting temperatureof the magnetic layer close to but slightly below the workingtemperature of the antiferromagnetic compound. This can be readilyachieved by employing a thermostatically, controlled heating or coolingdevice. Thus, in the apparatus of FIGS. 2 or 4, the working temperatureis higher than T and in the apparatus of FIG. 3 the working temperatureis T In the apparatus of FIG. 3, those portions of the layer I whichapproach the exposure station are maintained below the Neel-temperature,i.e., at a temperature which equals room temperature or at a temperaturewhich exceeds room temperature but is less than T Therefore, suchportions of the layer 1 are nonmagnetic and exhibit a low specific heat.The exposure of such layer portions to slightly elevated temperatureduring travel past the objective 6, i.e., the admission of relativelysmall amounts of heat energy, suffices to heat selected areas of thelayer to T and to thus produce in such areas a pronounced coercive forceH The exact metering of maximum heat supply is not critical because thespecific heat of the areas which are heated to or close to T increasessubstantially and, due to the aforediscussed anomaly of specific heatchanges (the compound tends to remain at or close to T longer than atanother temperature), the image receiving surface receives a highlysatisfactory thermal image of the original. The thermal image remainsintact for a reasonably long interval of time because the specific heatchanges in the region of T are slow.

The situation is analogous in the apparatus of FIGS. 2 and 4. In theseapparatus, the layer 1 is maintained at T before it reaches the exposurestation. This can be achieved without a highly accurate temperaturecontrol because the specific heat changes of the layer 1 at T are slow.Thus, those portions of the layer 1 which approach the exposure stationexhibit a pronounced coercive force H The coercive force of areas whichare heated above T to such an extent that their specific heat decreasesimmediately exhibit a much weaker coercive force with the result thatthe thermal image is an accurate reproduction of the image of theoriginal 7.

Without further analysis,-the foregoing will so fully reveal the gist ofthe present invention that others can, by applying current knowledge,readily adapt it for various applications without omitting featureswhich fairly constitute essential characteristics of the generic andspecific aspects of my contribution to the art and, therefore, suchadaptations should and are intended to be comprehended within themeaning and range of equivalence of the claims.

What is claimed as new and desired to be protected by Letters Patent isset forth in the appended claims:

1. A method of reproducing images of originals on transfer materialcomprising the steps of exposing a thermal image of an original onto animage receiving surface containing an ingredient which isantiferromagnetic'at temperatures above and below the Neel temperaturethereof, whose Neel temperature exceeds room temperature, and whichexhibits a pronounced coercive force at said Neel temperature, saidexposing step comprising changing the temperature of said surface inaccordance with the image pattern of the original so that said surfaceexhibits first areas which are maintained at said Neel temperature andsecond areas which are maintained at other than said Neel tempera ture;and converting said thermal image into a powder image includingcontacting said image receiving surface with a magnetic toner.

2. A method as defined in claim 1, wherein said ingredient is FeRh.

3. A method as defined in claim 1, further comprising the step ofmaintaining said ingredient below said Neel temperature prior to saidexposing step, said temperature changing step comprising heating saidfirst areas of said surface to said Neel temperature and said othertemperature being substantially below said Neel temperature.

4. A method as defined in claim 1, further comprising the step ofmaintaining said ingredient at said Neel temperature prior to saidexposing step, said temperature changing step comprising heating saidsecond areas above said Neel temperature so that said other temperaturesubstantially exceeds said Neel temperature.

5. A method as defined in claim 1, further comprising the step ofmaintaining said ingredient prior to said exposing step at a temperaturewhich closely approximates the temperature of one of said first andsecond areas upon completion of said temperature changing step.

6. A method as defined in claim 1, further comprising the step oftransferring said powder image onto a transfer material.

7. A method as defined in claim 1, wherein said contacting stepcomprises contacting the exposed image receiving surface with a coat ofpulverulent magnetic toner carried on a donor surface from which saidcoat the image receiving surface removes toner so that the thus removedtoner adheres to said first area of said image receiving surface and theremainder of said coat constitutes said powder image.

8. A method as defined in claim 1, further comprising the step oftransferring said thermal image of said image recieving surface onto amagnetic layer whose coercive force is less than the coercive force ofsaid ingredient at said Neel temperature, said contacting stepcomprising placing said transferred thermal image at least once intocontact with a pulverulent magnetic toner to thus convert said thermalimage into a powder image.

9. A method as defined in claim 1, wherein said toner consists ofpigmentized thermoplastic material and magnetizable carrier for saidpigmentized thermoplastic material.

10. A method as defined in claim 9, further comprising the steps oftransferring said powder image onto a transfer material and fixing thetransferred powder image to the transfer material in the presence ofheat. l=

2. A method as defined in claim 1, wherein said ingredient is FeRh.
 3. Amethod as defined in claim 1, further comprising the step of maintainingsaid ingredient below said Neel temperature prior to said exposing step,said temperature changing step comprising heating said first areas ofsaid surface to said Neel temperature and said other temperature beingsubstantially below said Neel temperature.
 4. A method as defined inclaim 1, further comprising the step of maintaining said ingredient atsaid Neel temperature prior to said exposing step, said temperaturechanging step comprising heating said second areas above said Neeltemperature so that said other temperature substantially exceeds saidNeel temperature.
 5. A method as defined in claim 1, further comprisingthe step of maintaining said ingredient prior to said exposing step at atemperature which closely approximates the temperature of one of saidfirst and second areas upon completion of said temperature changingstep.
 6. A method as defined in claim 1, further comprising the step oftransferring said powder image onto a transfer material.
 7. A method asdefined in claim 1, wherein said contacting step comprises contactingthe exposed image receiving surface with a coat of pulverulent magnetictoner carried on a donor surface from which said coat the imagereceiving surface removes toner so that the thus removed toner adheresto said first area of said image receiving surface and the remainder ofsaid coat conStitutes said powder image.
 8. A method as defined in claim1, further comprising the step of transferring said thermal image ofsaid image recieving surface onto a magnetic layer whose coercive forceis less than the coercive force of said ingredient at said Neeltemperature, said contacting step comprising placing said transferredthermal image at least once into contact with a pulverulent magnetictoner to thus convert said thermal image into a powder image.
 9. Amethod as defined in claim 1, wherein said toner consists of pigmentizedthermoplastic material and magnetizable carrier for said pigmentizedthermoplastic material.
 10. A method as defined in claim 9, furthercomprising the steps of transferring said powder image onto a transfermaterial and fixing the transferred powder image to the transfermaterial in the presence of heat.